Snow ploughs



W. I. J. PRICE SNOW PLOUGHS Oct. 1, 1963 9 Sheets-Sheet 1 Filed Oct. 23, 1961 W. I. J. PRICE Oct. 1, 1963 SNOW PLOUGHS 9 Sheets-Sheet 3 Filed Oct. 23, 1961 Oct. 1, 1963 w. 1. .1. PRICE 7 3,105,312

SNOW PLOUGHS Filed Oct. 23, 1961 9 Sheets-Sheet 4 Oct. 1, 1963 w. 1. J. PRICE 3,105,312

SNOW PLOUGHS Filed Oct. 23, 1961 9 Sheets-Sheet 6 .SYAIBOL I Q /Q -/7 I O8 04 I I7 08 A lj/I/ /7 A /l/ -08 I l 0 /-o 2-0 W. I. J. PRICE SNOW PLOUGHS Oct. 1, 1963 9 Sheets-Sheet 7 Filed Oct. 23. 1961 0 xukwbikw V 2 F/QZ Oct. 1, 1963 Filed 001:. 25, 1961 4 MODEL/ W.- l. J. PRICE SNOW PLOUGHS 9 Sheets-Sheet 8 FPOMFULL SCALE 0 TEST! United States Patent 3,195,312 SNOW PLOUGHS William ldris James Price, Denham, England, assignor,

by rnesne assignments, to Council For Scientific and Industrial Research, London, England 7 Filed Oct. 23, 1%1, Ser. No. 147,009 Claims priority, application Great Britain Oct. 26, 195i) 6 Claims. (Cl. 37-47) This invention relates to snow ploughs of the V blade type which are adapted to be mounted on a propulsion vehicle by which they are driven through a mass of snow on a road or like surface to be cleared. Such ploughs consist of a blade having a pair of backward-divergent wings meeting in a sharply defined leading edge and which are usually (although not necessarily) symmetrical about the mean line of travel of the plough.

For snow ploughs of the V blade type, different conditions impose different design requirements. Thus, for shallow snowdefined herein as less than one foot deepthe rate of travel is usually relatively high, and the major requirement is for a good cast, i.e. the ability of the plough to throw the snow well to either side of the road. On the other hand, in deep snow conditions, where depths of up to 4 feet or more are encountered, the major requirement is a maximum value of propulsive force.

These different operating requirements lead to difierent design parameters. In the case of the clearance of shallow snow, the requirement of a good cast is realized when the included bow angle 20:, at the leading edge, is relatively large. In deep snow conditions, however, the minimum force is obtained when the included bow angle (20:), at the peak of the leading edge, is small. This invention is primarily concerned with snow ploughs suitable for the latter conditions.

There are two practical limitations to the indefinite reduction of the included bow angle 20:.

In the first place, progressive reduction of this angle leads to increased length of each wing, and hence the friction drag of the snow being penetrated increases owing to the larger surface area over which it must be made to flow.

In the second place, progressive reduction of 20: leads to increased overhang in the front of the propulsion vehicle, causingserious loss of maneuverability, and also an increased weight on the front axle of the vehicle where, as is more usual, this is a conventional wheeled vehicle rat-her than a tracked vehicle.

Hence, although there is no obvious theoretical lower limit to the value of 2a, practical operating conditions will place such a limitation on a design according to the present invention.

The problem of increased frictional drag with reduced bow angle 20c can be significantly reduced by giving each wing of the V a bl b, hard surface polish, or by coating the surface of each Wing with a low-friction substance such as P.T.F.E. or hard wax.

Snow ploughs of the fixed-V type are well-known, and their designs have hitherto possessed certain well-defined parameters as follows:

(i) Included bow angle (2d) at peak of leading edge: 7590.

(ii) Included foot angle (2gb) at base of leading edge: l20-150.

These known ploughs have been characterized in use by a marked tendency for causing the snow to pile up on the plough, and by the necessity for the use of relatively heavy powers for their propulsion through deep snow. The clearance of deep snow has consequently been a relatively ineflicient operation, and it is an object of the present invention to provide an improved design by which these disadvantages are materially reduced.

In a snow plough according to the present invention, the above-mentioned included angles are reduced to preferred values of the order of 2o=60 and 2=90, the permissible ranges being 2oc=5065 .and 2 =80l00. The upper section of each side is of part-cylindrical or part-conical form, the axis of the cylinder or cone being inclined forwards and downwards. This upper section blends tangentially into a front lower plane-section which makes an angle (1') to the horizontal of approximately 35say, in the range 32 /2 37 /z.

Advantageously, the front lower plane section terminates behind the vertical transverse plane through the peak.

The angle of the front lower plane section to the horizontal is also important from a practical point of view, since too high a value will cause the plough blade to tend to ride up out of the snow mass, while too low a value will cause it to tend to dig in and so to foul any surface irregularities of the road and to impose a heavy downward load on the front of the propulsion vehicle.

The performance of a snow plough on any scale can be defined in terms of the following dimensionless parameters:

termed the force factor;

termed the speed factor;

termed the depth factor; and

termed the efficiency.

where F=horizontal force on the plough in the direction of travel; usually ca led the draft;

g =acceleration due to gravity;

p :density of the snow;

I =the mean transverse width of v =the speed of the plough;

z =the height of the undisturbed surface of the snow above the bottom of the plough;

w=weight of snow removed by plough in moving forward a unit distance;

y :distance moved by centre of gravity of snow, normal to the line of travel of the plough;

n =overall efdciency of the plough.

Various analytical designs of snow plough and practical embodiments thereof in accordance with the present invention will now be particularly described with reference to the accompanying drawings in which:

FIGURE 1 is a perspective view of the basic planes governing the shape of a wing;

FIGURE 2 is a side elevation of a complete wing;

FIGURE 3 is a plan view of a plough with symmetrically disposed wings;

FIGURE 4 is a front elevation, seen in perspective;

FIGURE 5 is a rear elevation similar to FIGURE 4;

and

FIGURES 6-9 are a series of graphs of certain test results.

As can be seen from FIGS. 1-5 of the drawings, a plough according to the invention is of generally conventhe plough blade;

tional shape, being V-shaped in plan and usually-though not necessarilyadapted to be mounted on the pushing vehicle symmetrically with the mean line of travel. The particular manner of mounting the plough on a pushing vehicle or attaching the plough to a pushing vehicle is not an element of the instant invention. This can be done in any of several well-known manners, and normally the fitting of ploughs to vehicles is a task which is left to the contractor to deal with in the light of the particular vehicle concerned. Since the front end construction of propulsion vehicles varies widely according to size and manufacturer, it is impracticable to provide blades with standard mountings. Usually the work involved in mounting the plough concerns only the bolting or welding into position of one or more cross-members at appropriate points. For instance, such a cross-member is shown at in FIG- URE 3, and any number of these cross pieces may be utilized, arranged either in a common vertical plane or offset from each other with respect to a vertical plane. Quite often these cross-members are provided with fittings of well-known types to which arms from the pushing vehicle are bolted. Each wing 1 has two main sections, an upper cylindrical or conical section 2 and a front lower plane section 3. The plane section 3 is tangential to the cylindrical section 2.

FIGURE 1 illustrates in perspective the principal planes which represent the basic elements of the design. The plane OYWX is a vertical median plane containing the line of travel of the plough. The plane OYPM is a vertical plane tangential to the cylindrical or conical section 2 of the wing (FIGS. 24) and makes an angle at with the median plane OYWX. The plane OKN is also tangential to the curved section 2 of a wing 1 and is inclined to the hcrizontal at an angle 1-. The plane ONMX is horizontal. The front lower plane section 3 lies in the plane OKN, and the rearward edge of the plane section 3 is inclined upwards and rearwards as indicated at 4 in FIGURE 2. The vertical plane containing this edge 4 is represented in FIGURE 1 by the plane MKN and, if produced forwards (as indicated by the chain line NG), intersects the median plane OYWX at infinity or on a line well in advance of the front of the plough. This angle of intersection is designated a. (The lines NG and OS are deliberately distorted in FIGURE 1 to bring the meeting point G within the ambit of the drawing.)

The axis of the cylinder or cone on which the upper section 2 lies is inclined forwards and downwards so that the top edge of the plough rises from the peak 6 to the top 7 of the rear edge. A web or gusset plate 8 is welded into the apex of the V, where the two wings 1 meet, and serves to strengthen the blade. It has no great effect on performance.

The following quantities are used to define the shape of the plough: Y

'The shape of 'a plough according to the present in-vention can then be defined by the following values and The following proportions are also preferably maintained:

r/l-0.23 to 0.30 (0.27) h /l-0.46 to 0.54 (0.48) h /lO.66 to 0.80 0.72

Usually I will have values in the range 5 ft. to 11 ft.

Plough blades of various shapes and surface finishes were compared by plotting, for each plough blade, values of force factor F/g l and efliciency 1 against speed factor v /gl at a number of values of depth factor z/l. These values were obtained both by experimentswith to scale models, using wet sawdust as a substitute for snow, and by full scale experiments in snow. Samples of the results for three model plough blades are given in FIGS. 6 and 7. The geometrical characteritics of these blades, defined in terms of FIG. 1, are given in the Table 1 below:

Table 1 T d s T/l hi/Z hz/Z In the graphs (FIGS. 6 and 7 the capital Roman numerals 'l, II, III refer to the full sized blades, whereas the geometrically similar model blades are designated by I the lower case Roman numerals i, ii, 111.

ratios, the preferred values in each case being shown in brackets after the respective permissible ranges:

In the model tests summerised in FIG. 6, the coefficient of surface friction (,u.) between the plough blade and the sawdust had a value of about 0.37. It will be seen that the lowest draft is generally experienced With model ii but that the highest efiiciencies, 7], are given by blade iii.

Because of the small value of the semi-bow angle, or, i.e. 20, on blade iii it isdifiicult to mount such a plough on a conventional vehicle. Moreover, it overhangs the front of the vehicle by a considerable distance so that the maneuverability of the vehicle is greatly impaired.

Blade ii represents a reasonable compromise between a shape which has a low draft with high etficiency and one that can be mounted on a conventional truck without undue difiiculty.

The draft of a blade can be further reduced and the efiiciency increased by reducing the value of the methcient of surface friction (,u). To achieve this, the blade ii was coated with a P.T.F.E. film applied by spray at a high temperature. The effect on the draft and efliciency can be seen in FIGS. 6 and 7 by comparing the full lines for blade ii with the dotted lines at the same values of z/l.

The results of full scale tests are given below in Table 2. A comparison of these results with those from model tests are given in FIGS. 8 and 9. The plotted points refer to the full scale tests, whereas the lines were derived from model experiments. Within the limits of experimental error, there is reasonable agreement between values ob tained for draft (F/g l on model and prototype. This confirms that the order of merit determined from model tests in wet sawdust will be valid on the full scale in snow. It establishes the general superiority of blade ii over blade i. To some extent, this was evident from visual observation at the full scale trials. The snow tends to pile up ahead of blade I, but blade II, because of its more streamlined shape, sheds the snow sideways more easily.

A plough blade with the shape described in this specification may be made of metal, plastic, rubber or bonded glass fibre, or any combination of these materials. Its front-facing ploughing surfaces 2, 3 must have as smooth a finish aspossible and it should be coated with suitable material to give a low value for the coefi'icient of friction of the surface on snow. This further improves the performance of the plough. Suitable coating materials for a metal plough are P.T.F.E. and the epoxy or alkyl resins. The effect of the latter is enhanced by the application of a hard wax.

Table 2 BLADE I Snow Properties Depth Speed. Force Dimensionless of of on Parameters Plough- Plough- Plough Density Grain Cohesion Snow Surface ing 2, ing v, F/g. lb./ft. size (I, 0, Temp, Friction it. ftJs. lb. wt. 2/! v lgl F/flfll mm. 1b./in.' C. u

BLADE II I claim:

1. A snow plough having a blade of the V-type and means for supporting said blade on a propulsion vehicle, said blade comprising a pair of mutually inclined Wings each having an upper section curved about a generally horizontal axis and a lower plane section blending thereinto and inclined to the horizontal at an angle of the order of means for supporting said wings so that they intersect in a relatively sharp leading edge lying in a vertical plane when the plough is in its normal attitude on said vehicle, the angle between said Wings at the peak of said leading edge being of the order of 60 and at the foot of said edge being of the order of 4. A snow plough according to claim 3 wherein the ratio of said vertical height of said peak above the horizontal plane through said foot to said mean transverse width is 0.48.

5. A snow plough according to claim 1 wherein the ratio of the vertical height or" the top rear corners of said wings above the horizontal plane through said foot to said mean transverse width is of the order of 0.66 to 0.80.

6. A snow plough according to claim 5 wherein the ratio of said vertical height of said top rear corners above the horizontal plane through said foot to said mean transverse width .is 0.72.

90, and the ratio of the radius of said curved section References Cited in the file of this Patent of each wing to the mean transverse Width of the plough UN STATES PATENTS being of the order of 0.23 to 0.30.

2. A snow plough according to claim 1 wherein the 233 i3 ratio of said radius to said mean transverse width is 0.27.

3. A snow plough according to claim 1 wherein the FOREIGN PATENTS ratio of the vertical height of said peak above the hori- 46,063 Norway Feb. 4, 1929 zontal plane through said foot to said mean transverse 130,528 Sweden Jan. 16, 1951 width is of the order of 0.46 to 0.54. 821,470 Great Britain Oct. 7, 1959 

1. A SNOW PLOUGH HAVING A BLADE OF THE V-TYPE AND MEANS FOR SUPPORTING SAID BLADE ON A PROPULSION VEHICLE, SAID BLADE COMPRISING A PAIR OF MUTUALLY INCLINED WINGS EACH HAVING AN UPPER SECTION CURVED ABOUT A GENERALLY HORIZONTAL AXIS AND A LOWER PLANE SECTION BLENDING THEREINTO AND INCLINED TO THE HORIZONTAL AT AN ANGLE OF THE ORDER OF 35*; MEANS FOR SUPPORTING SAID WINGS SO THAT THEY INTERSECT IN A RELATIVELY SHARP LEADING EDGE LYING IN A VERTICAL PLANE WHEN THE PLOUGH IS IN ITS NORMAL ATTITUDE ON SAID VEHICLE, THE ANGLE BETWEEN SAID WINGS AT THE PEAK OF SAID LEADING EDGE BEING OF THE ORDER OF 60* AND AT THE FOOT OF SAID EDGE BEING OF THE ORDER OF 90*, AND THE RATIO RADIUS OF SAID CURVED SECTION OF EACH WING TO THE MEANS TRANSVERSE WIDTH OF THE PLOUGH BEING OF THE ORDER OF 0.23 TO 0.30. 